About four years ago I installed a B&M street & strip shift kit in my 700R4. I am an avid gm person and have done trans work wile working for GMC truck.I have had the same rpoblem from day one. If you shift it manually or leave it in D3 it shifts excellent. If you try it in drive under heavy load it will go into third and slip past into what sounds like clutch slippage. I have found nothing in GM trans manuals about this problem. Any ideas......thanks, Mike

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85, z28, tpi 5.0, numerous mods...the usual

 

-If you try it in drive under heavy load it will go into third and slip past into what sounds like clutch slippage.-

I don't understand where you are trying to say it slips.
Does it slip only in third when left in OD, or it slips in all gears when left in OD.

Did it work fine before you put the B&M kit in??

 

It slips only when it first shifts into 3rd, and it was fine before the kit. Once it is in 3rd it will shift fine into 4th

 

Is the TV cable setup right???
The early trans had alot of problems that were fixed later on(I assume your trans is 85 also). Transgo addresses this in the SK-700 kit. You get more than a spring and a drill bit!!

I would get rid of the B&M kit and put a Transgo kit in it. At least the valve body mods. I don't know what the B&M kit came with, but if you changed the 2nd apply piston, you may have knicked a seal.It will be the first (larger) seal on the inner most piston.

Also the #7 checkball capsule is notorious for leaking and causing 3rd gear problems.

Any wear or leaking seals on the 3-4 accumlator will cause problems. What was the hole size drilled to on the 3rd oil ???

No sense in dropping the pan to check this stuff unless you are going to put a real shift kit. It would also be a good time to check the 3rd oil pressure. It must be within 10 lbs of mainline pressure.

Hope this helps.

 

I am late for work so I don't have time to really get into this but toss the B&M stuff and get a TransGo Reprogramming kit. Hopefully the 3-4 frictions aren't toast yet. By the way, B&M does not make a Shift Kit.

 

Sounds like B&M isn't making such a good kit. I haven't seen transgo in the marketplace yet. Where could I find them and do they sell a complete renew kit? I figured this problem would get progressivly worse but it hasn't. I planned to just tear it down and overhal it......Thanks for the info.

 

If you are looking for the Trans-Go Performance Shift kits & related parts (I have everything in stock for the 700R4) then give me a call at 800 7763288 Mon-Sat 10-6 PST and I will answer any questions you have concerning your transmission.
Glad Too Help!!!

 

TransGo is actually geared towards professionals. B&M sell mostly to the innocents out there. TransGo does have a video in the consumer version of their Reprogramming Kits to help you along but they don't sell O/H kits since they are readily available. They just concentrate on what they do best.